Desaturase genes, enzymes encoded thereby, and uses thereof

Abstract

Disclosed are isolated polynucleotides encoding an omega-3 desaturase and a delta-12 desaturase, the enzymes encoded by the isolated polynucleotides, vectors containing the isolated polynucleotides, transgenic hosts that contain the isolated polynucleotides that express the enzymes encoded thereby, methods for producing the desaturase enzymes, and method of using the enzymes to make polyunsaturated fatty acids. The isolated polynucleotides are derived from a fungus, Saprolegnia diclina (ATCC 56851). In particular, omega-3-desaturase may be utilized, for example, in the conversion of arachidonic acid (AA) to eicosapentaenoic acid (EPA). Delta-12 desaturase may be used, for example, in the conversion of oleic acid (OA) to linoleic (LA). EPA or polyunsaturated fatty acids produced therefrom may be added to pharmaceutical compositions, nutritional compositions, animal feeds, as well as other products such as cosmetics.

1. An isolated nucleotide sequence comprising or complementary to a nucleotide sequence encoding a polypeptide having Δ12-desaturase activity, wherein the amino acid sequence of said polypeptide has at least 90% sequence identity to SEQ ID NO:42. 
     
     
       2. An isolated nucleotide sequence comprising or complementary to at least 90% of the nucleotide sequence of SEQ ID NO:41. 
     
     
       3. The isolated nucleotide sequence of  claim 2 , wherein said sequence is SEQ ID NO:41. 
     
     
       4. The isolated nucleotide sequence of  claim 2  or  3 , wherein said sequence encodes a functionally active desaturase which utilizes a polyunsaturated fatty acid as a substrate. 
     
     
       5. The isolated nucleotide sequence of  claim 1  or  2 , wherein said sequence is derived from  Saprolegnia diclina .